Aspects of the invention relate to a valve element for a condensate trap, in particular, a valve element comprising an expansion chamber having a variable axial length.
Condensate traps are commonly used in steam systems, in which circumstances they are usually referred to as steam traps. Their function is to discharge condensed water from the system without allowing steam to escape. If steam is lost from the system, this represents a waste of energy. Steam traps thus commonly comprise a valve which is responsive to the presence of condensate or steam in the vicinity of the valve, so that the valve opens when condensate is present and closes when steam is present.
One type of steam trap, known as a balanced pressure steam trap, comprises a valve body having an inlet and an outlet which are in fluid communication with a valve body chamber. Located within the valve body chamber is a valve element which includes a metal bellows having a valve closure member which cooperates with a valve seat to open and close the valve. The metal bellows is deformable in the axial direction (i.e. the valve opening and closing direction) and has a bellows cavity which is filled with a fluid/gas mixture. When the temperature of the bellows is cooled by condensate, the volume of the fluid/gas mixture reduces and the bellows axially contracts, moving the valve closure member away from the valve seat and allowing the condensate to exit through the outlet. When the condensate has been discharged, the steam enters the valve body chamber and increases the temperature of the bellows. This causes the fluid/gas mixture to expand and the bellows axially expands, thus pressing the valve closure member against the valve seat and preventing steam from leaving the system through the outlet.
The metal bellows of a known steam trap is made from a number of metal disks which are plasma welded to one another. Whilst this produces a satisfactory component, the manufacturing procedure is time consuming. Further, the metal bellows has many small crevices within which bacteria can grow, and which are difficult to clean. This makes the steam trap unsuitable for some applications where hygiene is particularly important.
Metal bellows are known which are made from a single piece of material by deforming the material to produce corrugations which provide the bellows configuration. Such bellows lack rigidity in the radial direction, and consequently have not been considered suitable for steam trap applications, in which precise alignment of the valve closure member with the valve seat is required.
Accordingly, embodiments of the invention aim to address at least some of the above problems to some extent.